All the older shows - TOS, TNG, DS9, VOY, ENT - take place in some weird variant timeline that split off from our universe in the mid-sixties. Among other things they're filled with events that never happened and they've accumulated a history that's, well, to use the phrase one more time, preposterous. Eugenics Wars in the 1990s, the Bell riots, a mad scientist inventing androids that the rest of civilization can't figure out for decades, drunk hillbilly geniuses building warp rocketships out of ICBMs, another mad scientist inventing a teleportation device that the whole galaxy uses without understanding it.